The present invention relates to a probe for use in an atomic force microscope which is used to scan the surface of a sample substrate. The probe has a sharp tip and scans at angstrom-level accuracy. At the same time, it can examine the shape of the sample surface by measuring the interaction, such as atomic force, which occurs between the probe and the sample surface (G. Binning et al. Phys. Rev. Lett. 56,930 (1986)).
The invention also relates to a method for measuring the atomic force which occurs between the probe and the sample substrate surface utilizing tunneling current. As in shown in FIG. 8, a known probe comprises a protrusion 150, a cantilever 151, and a cantilever support base 160. Metal 152 is deposited on the surface of the cantilever. Tunneling current 154, which occurs between a metal wire 153 with a sharp tip fixed on the probe and a metal film 152 on the surface of cantilever 151, can be measured by the probe's approaching the cantilever surface. If the interaction which occurs between the protrusion 150 and sample substrate 50 makes the cantilever bend, the distance between the metal wire and cantilever changes according to the degree of bend, and the values of the tunneling current varies as well (FIG. 9). According to the measurement of the tunneling current variation, it is apparent how much the cantilever is bent by measuring the tunneling current force, namely, how much atomic force is applied between the protrusion and the sample substrate.
However, in the system noted above, it is not only difficult to properly adjust the distance between the cantilever and the metal wire, but it also has a defect that is easily influenced by vibration. To solve these problems, Pitsch, among others, suggested the methods to measure atomic force as follows (M. Pitsch et al., Progr Colloid Polym Sci, 83,56 (1990)). The probe herein mentioned is defined as a probe for use in an atomic force microscope comprising a tunneling current measuring means.
As in shown FIG. 10, the surface of a known probe 200 having a tunneling current measuring means is covered with insulation 201, 202, and metal 203 is made deposited on the insulation 201, 202. The insulation 201 comprises polyvinylalcohol 201 and the other insulation comprises octadecyl-trichlorosilane (OTS) 202. The tip of the probe is of OTS only. The OTS film is 10 angstroms in thickness which allows the tunneling current to occur via OTS between the probe and the metal deposited on the probe. The conventional scanning tunneling microscope is designed to be able to measure the tunneling current between the sample substrate and the probe. Therefore, the scanning microscope can be utilized so as to detect the tunneling current which occurs between the probe and the deposited metal film. When a probe approaches the substrate surface, the organic film bends and the distance between the deposited film and the probe changes. Consequently, the flow of the tunneling current changes, which enables measurement of the atomic force between the sample substrate surface and the probe.
In the invention proposed by Pitsch, the adjustment of the probe is unnecessary and vibration does not give much influence upon the measurement. Additionally, Pitsch's invention enables shifting from a scanning tunneling electronic microscope to an atomic force microscope. However, the probe manufactured by Pitsch could not be put to practical use, because it had problems such as poor adherence between an organic film and metal film deposited on the probe which caused separation of deposited metal film during scanning on the sample substrate surface with the probe. Furthermore, since the manufacturing process of the probe was comprised of many different process, that invention could not provide high reproducibility in manufacturing the probe.